Back to EveryPatent.com
United States Patent |
5,777,174
|
Marchionni
,   et al.
|
July 7, 1998
|
Process for preparing perfluoropolyethers with bromo- or iodo-containing
end groups
Abstract
Process for preparing perfluoropolyethers with bromo- or iodo- containing
end groups, respectively, by subjecting a peroxidic perfluoropolyether to
thermal treatment, in the absence of UV radiation, at temperatures from
120.degree. C. to 280.degree. C. in the presence of bromo- or
iodo-containing compounds having, respectively, the following general
formulas:
T T' T" C Br
wherein T, T', T" equal to or different from each other are selected from
Br, F, H or R'.sub.f, wherein R'.sub.f is a perfluoroalkylic chain from 1
to 8 carbon atoms;
R R' R" C I
wherein R, R', R", equal to or different from each other can be I (iodine),
H, F, or R'.sub.f, wherein R'.sub.f has the meaning indicated above.
Inventors:
|
Marchionni; Giuseppe (Milan, IT);
Guarda; Pier Antonio (Nole, IT)
|
Assignee:
|
Ausimont S.p.A. (Milan, IT)
|
Appl. No.:
|
845146 |
Filed:
|
April 21, 1997 |
Foreign Application Priority Data
| Apr 23, 1996[IT] | MI96A0798 |
Current U.S. Class: |
568/615; 204/157.63; 525/326.4; 568/591; 568/604; 568/614 |
Intern'l Class: |
C07C 041/01 |
Field of Search: |
568/615,604,591,614
204/157.63
525/326.4
|
References Cited
U.S. Patent Documents
3810874 | May., 1974 | Mitsch et al. | 260/75.
|
4853097 | Aug., 1989 | Marchionni et al. | 204/157.
|
4973762 | Nov., 1990 | Tohzuka et al. | 568/615.
|
5144092 | Sep., 1992 | Marchionni et al. | 568/615.
|
5155282 | Oct., 1992 | Marchionni et al. | 568/615.
|
5288376 | Feb., 1994 | Oyama et al. | 204/157.
|
Primary Examiner: Geist; Gary
Assistant Examiner: Padmanaphan; Sreeni
Attorney, Agent or Firm: Nikaido Marmelstein Murray & Oram LLP
Claims
We claim:
1. Process for preparing perfluoropolyethers with bromo- or iodo-containing
end groups, respectively, by subjecting a peroxidic perfluoropolyether to
thermal treatment, in absence of UV radiations, at temperatures from
120.degree. C. to 280.degree. C. in the presence of bromo- or
iodo-containing compounds having respectively the following general
formulas:
T T' T" C Br
wherein T, T', T" equal to or different from each other are selected from
Br, F, H or R'.sub.f, wherein R'.sub.f is a perfluoroalkylic chain from 1
to 8 carbon atoms;
R R' R" C I
wherein R, R', R", equal to or different from each other can be I, H, F or
R'.sub.f, wherein R'.sub.f has the meaning indicated above.
2. Process for preparing perfluoropolyethers with bromo- or iodo-containing
end groups, respectively, according to claim 1, wherein in the
bromo-containing compound T.dbd.Br and T' and T", equal to or different
from each other, are Br, F, H or R'.sub.f ; wherein in the iodo-containing
compound R.dbd.R'.dbd.R".dbd.I.
3. Process for preparing perfluoropolyethers with bromo- or iodo-containing
end groups, respectively, according to claim 1, wherein in the
bromo-containing compound T.dbd.T'.dbd.T".dbd.Br; and in the
iodo-containing compound R.dbd.R'.dbd.H and R".dbd.I, or R.dbd.H and
R'.dbd.R".dbd.I.
4. Process for preparing perfluoropolyethers with bromo-containing or
iodo-containing end groups, respectively, according to claim 1, wherein
the perfluoropolyether comprises repeating units statistically distributed
along the chain, selected from: --CF.sub.2 O--, --CF.sub.2 CF.sub.2 O--,
--CF.sub.2 CF(CF.sub.3)O--, --CF(CF.sub.3)O--,
--CF.sub.2 (CF.sub.2).sub.z CF.sub.2 O--, --CF.sub.2 CF(OR.sub.f)O--, --CF
(OR.sub.f)O--,
wherein z=1 or 2, R.sub.f is --CF.sub.3, --C.sub.2 F.sub.5, or --C.sub.3
F.sub.7.
5. Process for preparing perfluoropolyethers with bromo- or iodo-containing
end groups, respectively, according to claim 4, wherein in the case of
iodo-containing end groups the iodo-containing end groups are selected
from --CF.sub.2 I, --CF.sub.2 CF.sub.2 I, --CFICF.sub.3, --CFIOR.sub.f,
wherein R.sub.f is defined as above;
in the case of bromo-containing end groups, the bromo-containing end groups
are selected from --CF.sub.2 Br, --CF.sub.2 CF.sub.2 Br, --CFBrCF.sub.3
and --CFBrOR.sub.f, wherein R.sub.f is defined as above.
6. Process for preparing perfluoropolyethers with bromo- or iodo-containing
end groups, respectively, according to claim 1, wherein in the case of
bromo-containing end groups the reaction temperature is comprised between
160.degree. C. and 230.degree. C.; in the case of iodo-containing end
groups between 130.degree. C. and 180.degree. C.
7. Process for preparing perfluoropolyethers with bromo- or iodo-containing
end groups, respectively, according to claim 4, wherein such
perfluoropolyethers having the number average molecular weight Mn of the
iodo- or bromo-containing derivatives is comprised from 400 to 4000, and
are selected from the following classes:
(a) T1--O(CF.sub.2 CF(CF.sub.3)O).sub.a (CFXO).sub.b --T2
wherein: T1 and T2 equal to or different from each other, are
bromo-containing end groups of the type --CF.sub.2 Br, --CFBrCF.sub.3 or
iodo-containing end groups of the type --CF.sub.2 I, --CFICF.sub.3 and
optionally also end groups of the type
I) --CF.sub.3, --C.sub.2 F.sub.5 and --C.sub.3 F.sub.7,
II) --CF.sub.2 COF, --OCOF, --CF.sub.2 COCF.sub.3 ;
III) ClCF.sub.2 CF(CF.sub.3)--, CF.sub.3 CFClCF.sub.2 --, ClCF.sub.2
CF.sub.2 --, ClCF.sub.2 --;
X is F or CF.sub.3 ; a and b are integers such that the molecular weight is
comprised in the range indicated above; a/b is comprised between 10 and
100;
(b) T3--O(CF.sub.2 CF.sub.2 O).sub.c (CF.sub.2 O).sub.d (CF.sub.2
(CF.sub.2).sub.z CF.sub.2).sub.h --T4
wherein T3 and T4, equal to or different from each other, are
bromo-containing end groups of the type --CF.sub.2 Br, --CF.sub.2 CF.sub.2
Br, or iodo-containing end groups of the type --CF.sub.2 I, --CF.sub.2
CF.sub.2 I, and optionally also end groups of the types I), II), III)
indicated above; c, d and h are integers such that the molecular weight is
comprised in the range indicated above; c/d is comprised between 0.1 and
10; h/(c+d) is comprised between 0 and 0.05, wherein z=1 or 2;
(c) T5--O(CF.sub.2 CF(CF.sub.3)O).sub.e (CF.sub.2 CF.sub.2 O).sub.f
(CF.XO).sub.g --T6
wherein T5 and T6, equal to or different from each other, are
bromo-containing end groups of the type --CF.sub.2 Br, --CF.sub.2 CF.sub.2
Br, --CFBrCF.sub.3 or iodo-containing end groups of the type --CF.sub.2 I,
--CF.sub.2 CF.sub.2 I, --CFICF.sub.3, and optionally also end groups of
the types I), II), III) indicated above; X is F or CF.sub.3 ; e, f, g are
integers such that the molecular weight is comprised in the range
indicated above; e/(f+g) is comprised between 0.1 and 10, f/g is comprised
between 2 and 10;
(d) T7--O(CF.sub.2 O).sub.j (CF.sub.2 CF(OR.sub.f)O).sub.k
(CF(OR.sub.f)O).sub.1 --T8
wherein: R.sub.f is --CF.sub.3, --C.sub.2 F.sub.5, --C.sub.3 F.sub.7 ; T7
and T8, equal to or different from each other, are bromo-containing end
groups of the type --CF.sub.2 Br, --CF.sub.2 CF.sub.2 Br, --CFBrOR.sub.f,
or iodo-containing end groups of the type --CF.sub.2 I, --CF.sub.2
CF.sub.2 I, --CFIOR.sub.f ; and optionally also end groups of the types
I), II), III) indicated above; j,k,l are integers such that the molecular
weight is comprised in the range indicated above; k+l and j+k+l are at
least equal to 2, k/(j+l) is comprised between 0.01 and 1000, l/j is
comprised between 0.01 and 100.
8. Process for preparing perfluoropolyethers with bromo- or iodo-containing
end groups, respectively, according to claim 7, wherein the obtained
product is submitted to chromatographic separation on silica gel.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for preparing perfluoropolyethers
with bromo- or iodo-containing end groups, respectively.
2. Description of the Related Art
As known, these products can be utilized as additives in rubber mixtures
curable with peroxides and as removers of the fluoroelastomers molds in
the case of bromo-containing products, and as intermediates useful for the
synthesis of fluoro-containing resins, fluoro-containing elastomers and
fluoro-containing surfactants in the case of iodo-containing products.
It is known in the art that it is possible to prepare perfluoropolyethers
with bromo-containing end groups with good yields and with controlled
molecular weight utilizing perfluoropolyethers having both linear and
branched chain by submitting a peroxidic perfluoropolyether to photolysis
with UV radiations in the presence of bromine at temperatures comprised
from -40.degree. to +130.degree. C. in the presence or not of an inert
solvent. See for instance U.S. Pat. No. 5,155,282. In this patent it is
specified that if one works in absence of UV radiations in a wide range of
temperatures, low yields in bromo-containing product are obtained and
without any control of the molecular weight. The process of preparation
indicated in the patent mentioned above involves therefore the utilization
of UV radiations and therefore expensive processes and plants.
Other methods for preparing products with halogen containing end groups are
known in the art. For instance end groups are obtained wherein the halogen
can be bromine, iodine or chlorine starting from the silver salt of the
perfluoropolyethers acid. See for instance U.S. Pat. No. 3,810,874.
In the patent EP 151,877 a method for preparing perfluoropolyethers with
chloro- or bromo-containing end groups is described, by starting from
perfluoropolyethers with hydrogen-containing end groups by reaction with
chlorine or bromine to obtain chloro- or bromo-containing derivatives.
In the patent EP 348,948 one starts from acylfluoride of a
perfluoropolyether and the salt is prepared by reaction with a carbonate
and further reaction with iodine to obtain a perfluoropolyether with
iodo-containing end groups.
In the patent EP 472,423 it is described a process similar to that of EP
'948 wherein acylfluoride is reacted with a metal iodide to prepare
acyliodide and subsequent treatment with UV radiations to obtain
perfluoropolyether with iodo-containing end groups.
In the U.S. Pat. No. 4,853,097 in the name of the Applicant one starts from
an acylfluoride of a perfluoropolyether, which is reacted with ammonia and
then with hypobromite to obtain a derivative with bromo-containing end
group.
In all these patents of the prior art either UV radiations are utilized
which imply expensive plants or it is to be started from functionalized
perfluoropolyethers requiring transformation reactions for their
obtainment. Also in this case, the industrial processes which can be
carried out require additional steps and therefore higher production
costs.
It was felt the need to have available a process for preparing
perfluoropolyethers with bromo- or iodo-containing end groups
respectively, which removed the drawbacks of the known art and allowed to
have a simplified and therefore less expensive process available.
SUMMARY OF THE INVENTION
The Applicant has now unexpectedly and surprisingly found that it is
possible to obtain with good yields perfluoropolyethers with bromo- or
iodo-containing end groups and at the same time to obtain a control of the
molecular weight with the process of the invention described hereunder by
starting from peroxidic perfluoropolyethers without utilizing UV
radiations.
An object of the invention is a process for preparing perfluoropolyethers
with bromo- or iodo-containing end groups, respectively, by submitting a
peroxidic perfluoropolyether to thermal treatment, in absence of UV
radiations, at temperatures comprised between 120.degree. C. and
280.degree. C. in the presence of bromo- or iodo-containing compounds
having respectively the following general formulas:
T T'T"C Br
wherein T, T', T" equal to or different from each other are selected from
Br, F, H or R'.sub.f, wherein R'.sub.f is a perfluoroalkylic chain from 1
to 8 carbon atoms, the case in which T=Br and T' and T", equal to or
different from each other, are Br, F, H or R'.sub.f, is preferred; an even
more preferred particular case is the one wherein T=T'=T"=Br;
R R'R"C I
wherein R, R', R", equal to or different from each other can be I (iodine),
H, F or R'.sub.f, wherein R'.sub.f has the meaning indicated above,
preferably R=R'=R"=I, or R=R'=H and R"=I, or R=H and R'=R"=I.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In particular the perfluoropolyether comprises repeating units
statistically distributed along the chain selected from:
--CF.sub.2 O--, --CF.sub.2 CF.sub.2 O--, --CF.sub.2 CF(CF.sub.3)O--,
--CF(CF.sub.3)O--, --CF.sub.2 (CF.sub.2).sub.z CF.sub.2 O--, --CF.sub.2
CF(OR.sub.f)O--, --CF(OR.sub.f)O--,
wherein z=1 or 2, R.sub.f is --CF.sub.3, --C.sub.2 F.sub.5, or --C.sub.3
F.sub.7.
In the case of perfluoropolyethers with iodo-containing end groups, the end
groups are selected from: --CF.sub.2 I, --CF.sub.2 CF.sub.2 I,
--CFICF.sub.3, --CFIOR.sub.f, wherein R.sub.f is defined as above; instead
in the case of bromo-containing perfluoropolyethers, the bromo-containing
end groups are selected from --CF.sub.2 Br, --CF.sub.2 CF.sub.2 Br,
--CFBrCF.sub.3 and --CFBrOR.sub.f, wherein R.sub.f is defined as above.
Optionally in the products obtained with the process of the invention, both
in the case of bromo- and iodo-containing end groups, also
perfluoropolyether products can be present, having end groups selected
from:
I) --CF.sub.3, --C.sub.2 F.sub.5 and --C.sub.3 F.sub.7,
II) --CF.sub.2 COF, --OCOF, --CF.sub.2 COCF.sub.3 ;
III) ClCF.sub.2 CF(CF.sub.3)--, CF.sub.3 CFClCF.sub.2 --, ClCF.sub.2
CF.sub.2 --, ClCF.sub.2 --.
In the case of bromo-containing end groups the preferred reaction
temperature is comprised between 160.degree. C. and 230.degree. C.; in the
case of iodo-containing end groups between 130.degree. C. and 180.degree.
C.
The average molecular weight of the product obtained with the process of
the present invention can be changed depending on the starting peroxidic
perfluoropolyether. In particular, the higher the content of peroxidic
units of the starting product, the lower is the average molecular weight
of the bromo-derivative or iododerivative obtained. This allows to adjust
the molecular weight of the product obtained by changing the
characteristics of the starting product. The content of peroxidic units is
generally expressed as PO, defined as PO=g active oxygen/100 g of polymer,
by meaning as active oxygen the oxygen atoms bound to another oxygen atom.
The number average molecular weight Mn of the iodo- or bromo-containing
derivatives according to the present invention is generally comprised from
400 to 4000.
In particular perfluoropolyoxyalkylenes can be selected from the following
classes:
(a) T1--O(CF.sub.2 CF(CF.sub.3)O).sub.a (CFXO).sub.b --T2
wherein: T1 and T2 equal to or different from each other, are
bromo-containing end groups of the type --CF.sub.2 Br, --CFBrCF.sub.3 or
iodo-containing end groups of the type --CF.sub.2 I, --CFICF.sub.3 and
optionally also end groups of the type I), II), III) indicated above; X is
F or CF.sub.3 ; a and b are integers such that the molecular weight is
comprised in the range indicated above; a/b is comprised between 10 and
100.
(b) T3--O(CF.sub.2 CF.sub.2 O).sub.c (CF.sub.2 O).sub.d (CF.sub.2
(CF.sub.2).sub.z CF.sub.2).sub.h --T4
wherein T3 and T4, equal to or different from each other, are
bromo-containing end groups of the type --CF.sub.2 Br, --CF.sub.2 CF.sub.2
Br, or iodo-containing end groups of the type --CF.sub.2 I, --CF.sub.2
CF.sub.2 I, and optionally also end groups of the types I), II), III)
indicated above; c, d and h are integers such that the molecular weight is
comprised in the range indicated above; c/d is comprised between 0.1 and
10; h/(c+d) is comprised between 0 and 0.05.
(c) T5--O(CF.sub.2 CF(CF.sub.3)O).sub.e (CF.sub.2 CF.sub.2 O).sub.f
(CFXO).sub.g --T6
wherein T5 and T6, equal to or different from each other, are
bromo-containing end groups of the type --CF.sub.2 Br, --CF.sub.2 CF.sub.2
Br, --CFBrCF.sub.3 or iodo-containing end groups of the type --CF.sub.2 I,
--CF.sub.2 CF.sub.2 I, --CFICF.sub.3, and optionally also end groups of
the types I), II), III) indicated above; X is F or CF.sub.3 ; e, f, g are
integers such that the molecular weight is comprised in the range
indicated above; e/(f+g) is comprised between 0.1 and 10, f/g is comprised
between 2 and 10.
(d) T7--O(CF.sub.2 O).sub.j (CF.sub.2 CF(OR.sub.f)O).sub.k
(CF(OR.sub.f)O).sub.l --T8
wherein: R.sub.f is --CF.sub.3, --C.sub.2 F.sub.5, --C.sub.3 F.sub.7 ; T7
and T8, equal to or different from each other, are bromo-containing end
groups of the type --CF.sub.2 Br, --CF.sub.2 CF.sub.2 Br, --CFBrOR.sub.f,
or iodo-containing end groups of the type --CF.sub.2 I, --CF.sub.2
CF.sub.2 I, --CFIOR.sub.f ; and optionally also end groups of the types
I), II), III) indicated above; j,k,l are integers such that the molecular
weight is comprised in the range indicated above; k+l and j+k+l are at
least equal to 2, k/(j+l) is comprised between 0.01 and 1000, l/j is
comprised between 0.01 and 100.
The peroxidic perfluoropolyethers utilized as starting products and
comprising the repeating units indicated above are well known in the art,
for instance see patents U.S. Pat. No. 3,665,041, 2,242,218, 3,715,378 and
patents EP 239,123, EP 344,547, U.S. Pat. No. 5,144,092. Peroxidic
perfluoropolyethers generally have number average molecular weight from
1,600 to 100,000, preferably from 3,000 to 50,000; PO is generally
comprised between 0.2 and 4.0, preferably between 2 and 3.5.
With the process of the invention in the case of bromo-containing end
groups, the yields are very high, of the order of 50-90% by weight, more
generally of the order of 80-90% by weight. In the case of iodo-containing
end groups, the yields are of about 50-70% by weight.
As already said above, to obtain perfluoropolyethers with bromo-containing
end groups by the process of the present invention, the peroxidic
perfluoropolyether is reacted with bromo-containing compounds of general
formula T T'T"C Br as defined above.
As already said above, to obtain perfluoropolyethers with iodo-containing
end groups by the process of the present invention, the peroxidic
perfluoropolyether is reacted with iodo-containing compounds having the
general formula R R' R"C I as defined above.
The products obtained by the process of the present invention generally
comprise mixtures of alpha, omega-diiodo and monoiodo perfluoropolyethers
in the case of preparation of perfluoropolyethers with iodo-containing end
groups; or alpha, omega-dibromo perfluoropolyethers and monobromo
perfluoropolyethers in the case of preparation of perfluoropolyethers with
bromo-containing end groups.
The functionality f of the final product in bromo- or iodo-containing end
groups is defined, as:
f=2 . (iodo- or bromo-containing end groups)/total end groups.
The functionality f will have the value of 2 when all the end groups are
iodo- or bromo-containing end groups. From the reaction mixture it is
extremely easy, if desired, to carry out the separation of the diiodo- or
dibromo-containing product, for instance by chromatographic separation for
instance on silica gel, from the optional perfluoropolyethers containing
fluoroacylic end groups.
It is thus possible to obtain the diiodo- or dibromo-containing product
with high functionality with global yields depending on the relative
percentage of iodo- or bromo-containing end groups and fluoroacylic end
groups obtained during the synthesis.
For instance, as regards the iodo-containing products obtained after the
thermal treatment of the peroxidic perfluoropolyoxyalkylene in the
presence of the iodo-containing compounds of the present invention, they
are formed of alpha, omega-diiodoperfluoropolyethers in admixture with
alpha-iodoperfluoropolyethers and with perfluoropolyethers not containing
iodine. The end groups formed during the treatment of the peroxidic
perfluoro-polyether with the iodo-containing compound of the present
invention are indeed only constituted by iodo-containing end groups and by
end groups of acylfluoride type (--COF). Obviously in the final product
are present also the original end groups of the starting peroxidic
perfluoropolyether, which can be end groups of type I), II) or III), as
defined above. Therefore, if a high functionality product in
iodo-containing end groups is desired to be prepared, it is sufficient to
start from a peroxidic perfluoropolyoxyalkylene having a sufficiently high
average molecular weight so that the original end groups of the peroxidic
perfluoropolyoxyalkylene are worthless. Subsequently it is sufficient to
submit the mixture to chromatographic separation on silica gel or other
stationary phase capable of holding the products having an acid character.
In particular the end groups --COF can be hydrolyzed to end groups --COOH,
for instance by reaction with water according to the methods described in
U.S. Pat. No. 3,810,874, then to dissolve the mixture in a solvent and
percolate the solution in a column packed with silica gel to obtain a
product substantially consisting of alpha, omega-diiodoperfluoropolyethers
and then having a high functionality (defined as above) in iodo-containing
end groups.
Similarly this is valid also for the bromo-containing products obtained by
the process of the present invention. In this case both the yield and the
selectivity in alpha, omega-dibromo derived with the process of thermal
treatment in the presence of the bromo-containing compound of the present
invention is very high, also >90%.
As already said the products with bromo-containing end groups obtained
according to the present invention can be used as removers from the
fluoroelastomers molds. The fluoroelastomers processing time is thus
reduced and the global productivity of the fluoroelastomers processability
is therefore increased.
The product obtained with iodo-containing end groups according to the
present invention is utilized as already said, as intermediate according
to what previously reported.
The following examples are given for illustrative purposes and are not
limitative of the scope of the present invention.
EXAMPLE 1
In a flask equipped with refrigerant and magnetic stirrer, 20.8 g of
peroxidic perfluoropolyether are introduced, having structure TO(CF.sub.2
CF.sub.2 O).sub.c (CF.sub.2 O).sub.d (O).sub.p T, with p integer such as
to give an average peroxidic power PO=1.93 (by PO it is meant the grams of
active oxygen, 16 amu, for 100 g of polymer); c and d are integers such
that the average ratio c/d=0.92 and such as to give a number average
molecular weight equal to 10,000; T is equal to CF.sub.3, COF. Then 8.2 g
of diiodomethane (CH.sub.2 I.sub.2) are added; it is kept under stirring
and gradually heated up to 170.degree. C.
It is maintained at 170.degree. C. for two hours and then at 180.degree. C.
for five hours.
The clear higher phase is separated (17 g), the iodometric analysis shows
PO=0 and the .sup.19 F-NMR analysis shows the following structure:
T3--O(CF.sub.2 CF.sub.2 O).sub.c (CF.sub.2 O).sub.d --T4
wherein T3 and T4 are --CF.sub.2 I, --CF.sub.2 CF.sub.2 I, --COF,
--CF.sub.2 COF, and traces of end groups CF.sub.3 ; the acid end
groups/iodo-containing end groups ratio is equal to 1.5. The c/d ratio is
equal to 0.62 and the number average molecular weight is equal to 1280
amu.
The so obtained product is hydrolyzed with water to transform the
fluoroacylic end groups into carboxylic acid end groups; diluted then in
1,1,2-triclorotrifluoroethane it is percolated in a column packed with
silica gel, in order to separate the alpha, omega-diiodo-containing
products from the monoacid or diacid products. The alpha,
omega-diiodo-containing products are thus quantified after distillation of
the solvent and result to be 15% by weight with respect to the initial
mixture. The .sup.19F -NMR analysis shows a complete absence of acid end
groups, c/d ratio equal to 0.71 and number average molecular weight equal
to 1300.
The percentage of diiodo-containing compound from the reaction mixture
results in strict agreement with the value determined on the basis of the
assumption that the end groups are statistically distributed among the
various polymeric chains.
The value determined on the basis of the probabilities results to be:
______________________________________
alpha, omega-diiodinated
(0.4).sup.2 .times. 100 = 16%
alpha, omega-diacylfluoride
(0.6).sup.2 .times. 100 = 36%
alfa-iodinated, omega-acylfluoride
2 .times. 0.4 .times. 0.6 .times. 100
______________________________________
= 48%
Therefore the perfluoropolyethers comprising iodo-containing end groups
result to be 64%.
EXAMPLE 2
In a flask equipped with refrigerant and magnetic stirrer, 25.6 g of
peroxidic perfluoropolyether are introduced, having structure TO(CF.sub.2
CF.sub.2 O).sub.c (CF.sub.2 O).sub.d (O).sub.p T, with PO=3.18, c/d
ratio=3.5 and number average molecular weight equal to 43,000; T has the
meaning indicated in Example 1. Then 13.1 g of iodoform (CHI.sub.3) are
added, it is kept under stirring and gradually heated up to 150.degree. C.
and maintained 2 hours at this temperature.
It is cooled and the higher phase, equal to 19.1 g, is separated. The
iodometric analysis shows PO=0 and the .sup.19 F-NMR analysis shows a
structure similar to that of Example 1, with the acid end
groups/iodo-containing end groups ratio equal to 1.2. The c/d ratio is
equal to 2.23 and the number average molecular weight is equal to 980.
The mixture is submitted as in Example 1 to hydrolysis and chromatographic
separation, obtaining an amount of alpha, omega-diiodoperfluoroethers
equal to 20% by weight with respect to the initial mixture, having number
average molecular weight equal to 950.
EXAMPLE 3
In a flask equipped with refrigerant and magnetic stirrer, 503 g of
peroxidic perfluoropolyether are introduced, having structure TO(CF.sub.2
CF.sub.2 O).sub.c (CF.sub.2 O).sub.d (O).sub.p T, with PO=3.18 (therefore
the peroxidic perfluoropolyether contains 1 mole of peroxidic bonds
--OO--), c/d ratio=3.5 and number average molecular weight equal to
43,000; T has the meaning indicated in Example 1; the kinematic viscosity
at 20.degree. C. equal to 17,600 cSt. 101 g of carbon tetrabromide
(CBr.sub.4 0.30 moles) are then introduced and then it is kept under
stirring.
It is heated with oil bath at 160.degree. C. for 3 hours, at 170.degree. C.
for 5 hours, at 180.degree. C. for 8 hours and at 190.degree. C. for 10
hours. During such a treatment the progressive decrease of the solid
reactant (CBr.sub.4) is observed until complete disappearance; at
190.degree. C. a remarkable liquid reflux occurs in the refrigerant
wherefore it is not possible to further increase the temperature in the
reactor to eliminate the residual traces of peroxide. The refrigerant is
then replaced by a claisen and the temperature increased up to 240.degree.
C. and maintained for 4 hours, distilling 68.7 g of product. The residue
is equal to 338 g.
By iodometric analysis the PO both of the distillate and of the residue
results 0.
The .sup.19 F-NMR analysis shows that both the distillate and the residue
have the following structure:
T3O--(CF.sub.2 CF.sub.2 O).sub.c (CF.sub.2 O).sub.d T4
wherein T3 and T4 are --CF.sub.2 Br, --CF.sub.2 CF.sub.2 Br and traces of
--CF.sub.2 COF and --CF.sub.3 ; the ratio between the end groups CF.sub.2
Br/CF.sub.2 CF.sub.2 Br is equal to 90:10.
The number average molecular weight of the distillate results equal to 530,
with c/d ratio=2.49 and functionality in bromo-containing end groups
f=1.92; the residue has number average molecular weight equal to 1370, the
c/d ratio is equal to about 2.09 and the functionality in bromo-containing
end groups is equal to 1.91.
The total yield in product with bromo-containing end groups is 81% by
weight.
EXAMPLE 4
With the same procedure as that utilized in Example 3, 219 g of peroxidic
perfluoropolyether are introduced in the reactor, having the structure
TO(CF.sub.2 CF.sub.2 O).sub.c (CF.sub.2 O).sub.d (O).sub.p T, with PO=2.04
and kinematic viscosity at 20.degree. C. equal to 38,000 cSt, the c/d
ratio is 1.7, T has the meaning of Example 1. 67 g of CBr.sub.4 (0.20
moles) are added and it is heated under stirring at 180.degree. C. for 9
hours, at 190.degree. C. for 11 hours and at 200.degree. C. for 4 hours.
It is cooled and the solid residue is separated by filtering. The product
is then treated at 230.degree. C. for 3 hours to eliminate the peroxide
traces.
177 g of product having PO=0 and structure similar to that of Example 3,
are obtained. The number average molecular weight determined by .sup.19F
-NMR results equal to 1900, the c/d ratio is equal to 1.13 and the
functionality in bromo-containing end groups is equal to 1.90.
EXAMPLE 5
With the same procedure as that utilized in Example 3, 521 g of the
peroxidic perfluoropolyether utilized in Example 4 are introduced in the
reactor. 91.5 g of CBr.sub.4 (0.28 moles) are added and heated under
stirring at 180.degree. C. for 4 hours, at 190.degree. C. for 4 hours and
at 200.degree. C. for further 4 hours and then at 210.degree. C. for
further 4 hours. The solid residue is separated by filtering and is
treated at 230.degree. C. for 4 hours to eliminate the residual peroxide
traces.
480 g of product (yield 92% by weight), having PO=0 and the same structure
as that of Example 3, are obtained. The number average molecular weight
(via .sup.19F -NMR) results equal to 1650 and the ratio between end groups
of the type --CF.sub.2 Br and --CF.sub.2 CF.sub.2 Br is equal to 94:6; the
c/d ratio is equal to 0.99 and the functionality in bromo-containing end
groups is equal to 1.90.
EXAMPLE 6
With the same procedure as that of Example 3, 20.7 g of peroxidic
perfluoropolyether are introduced in the reactor, having the structure
TO(CF.sub.2 CF.sub.2 O).sub.c (CF.sub.2 O).sub.d (O).sub.p T,
with PO=3.7, c/d ratio=4.98 and number average molecular weight equal to
9800, T being equal to CF.sub.3 and C.sub.2 F.sub.5. 5.3 g of CHBr.sub.3
are added and heated under stirring at 160.degree. C. for 6 hours, at
165.degree. C. for 15 hours, at 180.degree. C. for 4 hours, at 190.degree.
C. for 3.5 hours, at 200.degree. C. for 3.5 hours and at 230.degree. C.
for 4 hours. The two phases are separated and 10 g of product are
discharged, having PO=0 and structure similar to that of Example 3, with
T3 and e T4=--CF.sub.2 Br, --CF.sub.2 --CF.sub.2 Br, --CF.sub.2 COOH and
traces of --CF.sub.3 and --CF.sub.2 CF.sub.3 (deriving from the starting
peroxidic perfluoropolyether), the ratio between bromo-containing end
groups and --CF.sub.2 COOH end groups being equal to 4.1. The number
average molecular weight determined by NMR results equal to 900, the ratio
between --CF.sub.2 Br and --CF.sub.2 CF.sub.2 Br end groups is equal to
86:14, the c/d ratio=3.5 and the functionality in brominated end groups
f=1.4.
Top